Chiang Kai‐shek (31 October 1887 – 5 April 1975), also known as Jiang Zhongzheng and Jiang Jieshi, was a Chinese politician, revolutionary, and military leader who served as the leader of the Republic of China (ROC) and the Generalissimo from 1928 to his death in 1975 – until 1949 in Mainland China and from then on in Taiwan. Following the Kuomintang's defeat by the Chinese Communist Party in the Chinese Civil War, he continued to lead the ROC government in Taiwan until his death.

Born in Zhejiang, Chiang was a member of the Kuomintang (KMT), and a lieutenant of Sun Yat-sen in the revolution to overthrow the Beiyang government and reunify China. With help from the Soviets and the Chinese Communist Party (CCP), Chiang organized the military for Sun's Canton Nationalist Government and headed the Whampoa Military Academy. As commander-in-chief of the National Revolutionary Army (where he came to be known as a Generalissimo), he led the Northern Expedition from 1926 to 1928, before defeating a coalition of warlords and nominally reunifying China under a new Nationalist government. Midway through the Northern Expedition, the KMT–CCP alliance broke down and Chiang massacred communists inside the party, triggering a civil war with the CCP, which he eventually lost in 1949.

As the leader of the Republic of China in the Nanjing decade, Chiang sought to strike a difficult balance between modernizing China, while also devoting resources to defending the nation against the CCP, warlords, and the impending Japanese threat. Trying to avoid a war with Japan while hostilities with the CCP continued, he was kidnapped in the Xi'an Incident, and obliged to form an Anti-Japanese United Front with the CCP. Following the Marco Polo Bridge Incident in 1937, he mobilized China for the Second Sino-Japanese War. For eight years, he led the war of resistance against a vastly superior enemy, mostly from the wartime capital Chongqing. As the leader of a major Allied power, Chiang met with British Prime Minister Winston Churchill and U.S. President Franklin D. Roosevelt in the Cairo Conference to discuss terms for the Japanese surrender. When the Second World War ended, the Civil War with the communists (by then led by Mao Zedong) resumed. Chiang's nationalists were mostly defeated in a few decisive battles in 1948. In 1949, Chiang's government and army retreated to the island of Taiwan, where Chiang imposed martial law and persecuted critics during the White Terror. Presiding over a period of social reforms and economic prosperity, Chiang won five elections to six-year terms as President of the Republic of China in which he faced minimal opposition or was elected unopposed. Three years into his fifth term as president, and one year before Mao Zedong's death, he died in 1975. He was also director general of the Kuomintang until his death.

One of the longest-serving non-royal heads of state in the 20th century, Chiang was the longest-serving non-royal ruler of China, having held the post for 46 years. Like Mao, he is regarded as a controversial figure. Supporters credit him with playing a major part in unifying the nation and leading the Chinese resistance against Japan, as well as with countering CCP influence and economic development in both Mainland China and Taiwan. Detractors and critics denounce him as a brutal dictator, and often accuse him of being a fascist at the front of a corrupt authoritarian regime that suppressed civilians and political dissents, as well as flooding the Yellow River that subsequently caused the Henan Famine during the Second Sino-Japanese War. Other historians such as Jay Taylor argued that despite his many faults, Chiang's ideology notably differs from other authoritarian dictators of the 20th century and does not espouse the ideology of fascism. He argued that Chiang made genuine efforts to improve the economic and social conditions of mainland China and Taiwan such as improving women's rights and land reform. Chiang was also credited with transforming China from a semi-colony of various imperialist powers to an independent country by amending the unequal treaties signed by previous governments, as well as moving various Chinese national treasures and traditional Chinese artworks to the National Palace Museum in Taipei during the 1949 retreat, thus saving them from likely destruction.